This invention relates in general to servoactuator control systems and, more specifically, to an apparatus for computer control of remote servoactuators using a fiber optic information transmission system between a servoactuator interface and its controlling computer system.
A variety of different systems are used to operate, measure the position of, and control remote actuators, such as servoactuators, servovalves, solenoid valves and other servomechanisms. In aircraft, ships, machine tools and other applications these functions have generally been accomplished by hydraulic operating systems or mechanical linkages. While effective, these systems are heavy, occupy considerable space. Providing redundant control paths for safety is also quite difficult.
Recently, systems have come into use that use electrical signals passing through wires from input or control devices to the device, such as a flight control system, valve or the like. These so called "fly-by-wire" systems have come into widespread use in military aircraft and missiles. However, these systems are complex, a conventional electrically wired system requiring, typically, a servovalve, an actuator, valve position sensors and servovalve current sensing. Often, more that 25 conductors with attendant shielding is required. The weight, complexity, opportunity for breaks in wires or short circuits in these systems are significant problems. Also, these wired systems are subject to power failures, electromagnetic interference (EMI) from other nearby wiring or electrical devices and are subject to damage from electromagnetic pulses (EMP). There is a particular need to overcome these problems in military aircraft, missiles and ships as well as in numerical controlled machine tools and any other situation where EMI and EMP can be serious problems.
Considerable interest has developed in using optical fiber systems for remote control applications and for transmitting information rapidly and accurately over long distances. Fiber optics have many of the advantages of the fly-by-wire systems while being impervious to electrical shorts, EMI and EMP. Typical fiber optic control systems are disclosed by Sichling in U.S. Pat. No. 4,346,378 and Blackington in U.S. Pat. No. 4,313,226. While often effective, these systems tend to be electrically and optically complex with the mechanisms for measuring and controlling actuator position and transmitting corresponding optical signals being less than fully effective.
Thus, there is a continuing need for improved accurate, simple and effective servoactuation systems capable of accurately measuring the position of an actuator, reporting that position to a central computer interface and changing or correcting the actuator position as needed.